With reference to FIG. 9, a conventional latch assembly 400 used for disposing in an anti-fire door 500 comprises a tube body 410, a blocking member 420, a blocking pin 430, an elastic member 440 and a cover 450. The blocking member 420 and the cover 450 constrain the blocking pin 430 and the elastic member 440 in the tube body 410. High temperature results in melting of the blocking member 420 and makes the elastic member 440 pushing the blocking pin 430 to protrude to the tube body 410 when a fire accident occurs. The blocking pin 430 is wedged in the tube body 410 and a door frame 600 at the same time to make the anti-fire door 500 unable to be opened.
Owing to the blocking pin 430 disposed in the anti-fire door 500, the anti-fire door 500 and the blocking pin 430 produce deformation followed by environmental temperature variance of the fire scene. A space between the blocking pin 430 and the cover 450 used for accommodating the elastic member 440 instead becomes the space that allows the blocking pin 430 to retract back into the tube body 410.
The blocking pin 430 departs from the door frame 600 to make the latch assembly 400 unable to constrain the anti-fire door 500 to be unable to be opened when the blocking pin 430 deforms to make the blocking pin 430 retract back into the tube body 410.